The invention relates to a process for incorporating halogenated compounds into styrene polymer particles in aqueous suspension during the impregnation of the particles with a blowing agent.
Polymer foams are highly desirable in building construction because of their light weight and good heat insulating property. A prerequisite for use in the construction industry is the foam must have reduced flammability. Many halogenated organic compounds have been proposed as additives for the purpose of reducing the flammability of the foams.
In the case of expandable styrene polymer particles, the halogen compounds are often added to the particles by heating an aqueous suspension of styrene polymer particles in the presence of the halogen compound and a blowing agent until the particles are impregnated with the additives. Impregnation with the blowing agent to produce expandable styrene polymer particles may be carried out at temperatures between 60.degree. and 150.degree. C. However, when the organic halogen compounds are added to the impregnation system, lower temperatures, usually 60.degree.-90.degree. C., are used to prevent decomposition of the halogen compound which may in turn cause degradation of the polymer and subsequent impairment of the molding properties of the polymer. These lower temperatures require longer times for the impregnation process and, in the case of larger polymer particles, the particles may not be completely impregnated, as shown by the presence of hard cores in the particles after expansion. Shorter times of impregnation and the elimination of hard cores in the particles can both be accomplished by carrying out the impregnation at higher temperatures. It was, therefore, desirable to have a process for impregnation of styrene polymer particles with blowing agents at higher temperatures while still not detrimentally affecting the organic halogen compounds.